The aim of this study will be to identify small-molecule inhibitors of orphan nuclear receptor DAX-1 (NR0B1) through a HTS screening program. Inhibition of DAX-1 activity has a potential interest as a therapeutic tool in the domains of stem cell biology and cancer. Inhibitor screening will be performed by a simple transfection assay using as readout the relief of the transcriptional repressor activity of a Gal4 - DAX-1 C-terminal domain fusion on a luciferase reporter harboring Gal4 binding sites. Countersreen assays will subsequently involve the study of the activity of the hit molecules identified during the primary HTS campaign on DAX-1 transcriptional properties measured on a battery of DAX-1 responsive reporters, i.e. steroidogenic enzyme genes. Finally, tertiary assays will be aimed at developing compounds with improved DAX-1 inhibitor potency, assess their selectivity of action against other transcription factors and measure their toxicity. Furthermore, the efficacy of the inhibitors will be tested on DAX-1 - dependent growth of tumor cell lines. PUBLIC HEALTH RELEVANCE: Development of new drugs displaying increased selectivity and less toxicity is of utmost importance for modern anticancer therapy. Our project has the aim to search for new inhibitors for the orphan nuclear receptor DAX-1, which has a pivotal role in the growth of a specific type of soft tissue tumor of children and adolescents.